Titanium-niobium alloys



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This invention relates to titanium-niobium-base alloys, par-ticul-anly titanium rich and intermediate alloys containing up to 70 percent niobium.

This application is a continuation-in-part of our application Serial No. 575,937, filed April 4, 1956, now abandoned.

The binary titanium-niobium equilibrium diagram shows a beta-isomorphous system with -a limited solubility of niobium in alpha titanium and a rather extensive alpha-beta field. At 1100 F., about 3 percent niobium can be dissolved in alpha, while the alpha-beta field extends from about 3 to 35 percent niobium. On quenching from the beta field, beta is completely retained at 36 percent niobium and above. The addition of a third element to TiNb-base compositions provides further useful alloys.

It is an objective of this invention, therefore, to provide new and valuable titanium-niobium-base ternary alloys.

Still another object of this invention is to provide ternary alloys of titanium and niobium, and of titaniumniobium-base compositions, whereby valuable properties States Patent 3,933,798 Patented June 12, 1962 base ternary alloys containing up to 70 percent niobium, up to 45 percent of an alloying addition, balance titanium. Specific alloying elements of interest include vanadium, tantalum, and Zirconium. H

Binary alloys of titanium "and niobium have been prepared by melting in an inert tungsten-electrode arc furnace under a static argon partial pressure of 15 to 20 centimeters of mercury. Alloy compositions of 1.5 percent, 3 percent, '10 percent, 15 percent, 20 percent, 25 percent, 30 percent, percent, percent, percent, percent, and percent niobium, balance essentially all titanium have been prepared. Except for some spattering during the melting of the 60 percent and 70 percent niobium alloys, no difiiculties have been encountered in preparing these compositions. Alloy specimens containing up to 70 percent niobium have been fonged in air to a %-inch-square cross section. The forged ingots have been rolled in air at 1500 F. to approximately 0.040-inch sheet, using 10 percent reduction per pass. The alloys may then be given an annealing or stabilizing treatment.

Ternary titanium-niobium-base alloys have also been prepared by melting in an inert tungsten-electrode arc furnace under a static argon partial pressure of 15 to 20 centimeters. Table I lists mechanical properties of some ternary alpha-beta-type alloys. Data for binary Ti-lONb and Ti-lS'Nb compositions are included for comparison. The worked ternary alloys were all in the equilibrated-and-stabi-lized condition, i.e., held /2 hour at 1300 F., furnace cooled to l =F., held 1 hour and air-cooled.

Table I.Mechanical Properties of TiNb-Base Ternary Alpha-Beta Alloys Vickers hardness Yield strength, p.s.i. Elongation, per- Composition Number IO-kg. load Tensile cent in 1i.neh Reduc- Bend Weight percent strength tion in due- (balance Ti) (p.s.i.) area, tility As-cast Wrought 0.1% ofisct 0.2% ofiset Pni- Total percent orm of heat-treatability and useful strength-ductility relationships rnay be obtained and/or combined.

Yet another object of this invention is to provide effective titanium-niobium-base ternary compositions, with tantalum, zirconium, or vanadium as the third component.

Other objects and advantages of the present invention will be apparent from the following examples and detailed descriptions thereof.

in general, this invention rel-ates to titanium-niobium- An investigation of the aging properties of the alphabeta alloys has shown that alloys containing 10 percent niobium and 5 percent of another beta-stabilizing element have very high aging responses. In this investigation the ternary alpha-beta alloys were quenched from 1250 F. and 1550 F. and then aged at 800 F. for periods of time up to 16 hours. Alloys containing vanadium harden appreciably on quenching from either 1250 F. or 1550 F. Table 11 below shows the results of the aging studies in terms of hardness.

Table II.-Aging Response of Ternary TiNb-Base Alpha-Beta Alloys Aged a! 800 F.

11 they do at the lower temperatures. Thus, they provide useful high temperature alloys. Additions of from about 5 percent to about 45 percent of the elements to titaniumuench niobium alloys containin 30 to 70 ercent niobium are A Q g p ging Anoyweightpercentaddition time beneficiil. cgii itstangling hot hardnessfpropert es are ob hours VHNUO. VHN(1(). tamed y a ing 3 to 40 percent vanadium or zirconiuin to titanium-niobium alloys containing about 40 to 60 percent niobium. T140 V 233 Other alloy systems disclosed possess extremely valu- 1 317 806 able properties. For example Ti50N b-base alloys con- 2 gig taining vanadium andzirconium have excellent room- Ti 10 Nb 5 T 16 2g0 3 temperature ductility, very good uniform elongation, and a 2 2 3 improved strength at 1650 F. It is clear also that comgig plex alloys containing combinations of the individual al- 3 254 3 logilng elements will possess equally important and worth- 1 235 28 Ti-IO Nb-5 Zr 0 54( l 1 e pmpertles' 5 242 276 Table lV.-Hot Hardness of Ti-Nb Base Alloys 2 233 4 242 16 230 260 20 Hardness, DPH, kg./Ium. at temper- Composition, weight peratui'e F. indicated cent (balance Ti) 1} Specimens held at 1,250F. for 4 hours and water quenched prior to aging. 75 930 1,200 1,650

Specimens held at 1,550F. for 1 hour and water quenched prior to aging.

50 13s 94 40 19 These investigations indicate the value of alpha-beta- 146 107 66 40 type alloys containing from about 3 percent to about 2 3$ 52 percent niobium, from about 1 percent to about 10 199 162 100 42 percent of at least one of the alloying elements zirconium, S2 51* tantalum, vanadium, balance essentially titanium. The 304 282 242 178 data illustrate the useful properties of this alloy system. 30 E8 g9; g2 In addition to the alpha-beta-type alloys discussed 119 152 113 99 above, it has been found that titanium-ni0bium-base g8; ig 3 $3 ternary alloys of the beta type possess valuable proper- 249 198 149 121 ties and useful characteristics. Table III below lists the mechanical properties of these TiNb-base ternary B Elevated-temperature tests were conducted in a vacuum of less than 5 microns, using a load of 730 grams and an indentation time of 10 seconds alloys.

Table IlI.-Mechanzcal Properties of T-1Nbase Ternary Beta Alloys Vickers hardness Yield stregnth, p.s.i. Elongation, per- Reduc- Composition number 10-kg. load Tensile cent in 1 inch tion in Bend weight percent strength area, ductil- (balance Tl) (p.s.i.) perity As-cast Wrought 0.1% Ofiset 0.2% Offset Uniform Total cent 50 Nb 153 138 58, 000 58, 000 58,000 0 0 51 0 161 164 72, 000 72, 000 72, 000 10 47 0 219 109 83, 000 80, 000 13 17 42 O 266 272 106, 000 98, 000 98, 000 13 18 0 249 283 126, 000 118, 000 119, 000 13 17 48 0 285 304 141, 000 134, 000 135,000 3 3 8 1.0 360 390 177 140 63, 000 63, 000 63, 000 0 41 0 181 149 66, 000 65, 000 66, 000 0 16 54 0 50 Nb 202 179 74, 000 74, 000 74, 000 12 19 54 0 50 Nb- 207 206 50 Nb- 206 224 50 Nb- 169 233 50 Nb- 215 167 780,000 77,000 77,000 8 39 0 50 Nb 245 209 100, 000 95, 000 96, 000 9 13 40 0 50 Nb- 262 249 114,000 110, 000 110,000 13 20 55 0 50 Nb- 268 276 50 Nb-50 Zr--. 272 272 B Samples held 2 hours at 1,450 F. and water quenched.

Mechanical-property data for the Ti-SONb binary composition are included in the table for purposes of comparison. It should be noted that the ternary additions strengthened the base material. These alloys also show considerable increase in uniform elongation over the binary 50 percent niobium composition.

Hot-hardness data for the alloys are presented in Table IV. Values are tabulated for 75 F., 930 F., 1290 F., and 1650 F.

At 930 F. and 1290 F. vanadium gives the most effective strengthening per unit ternary addition, followed in order by zirconium and tantalum. However at 1650 F. the order is zirconium, vanadium and tantalum. At 20 percent addition and above, the ternary additions vanadium, zirconium, and tantalum strengthen much The data in Table V below show the results of tests to determine the resistance of the Ti--Nb base ternary alloys to oxidation in a static atmosphere at elevated temperatures. Specimens used in obtaining these data were about 0.25 x 0.50 X 0.04 inch and were prepared as follows: Each specimen was carefully finished on 400-grit paper, cleaned in a solvent, weighed and measured. Each specimen was then placed on a small ceramic ring and set in side a crucible cover. A second, larger ceramic ring was then placed around each specimen to insure retention of any spattered scale.

Each specimen assembly, prepared as described above, was placed on a firebrick and, thus supported, inserted into a furnace which had been brought up to the test temperature. The specimens were in this manner exmore, proportionately, at the higher temperatures than posed to air oxidation for periods of 16 hours at test tem peratures of 1400 F. and 1800 F. After exposure for the prescribed time, the treated specimens were covered with a second crucible cover and cooled. In this way, the loss of oxidation products during the cooling period was avoided.

After the specimens had been cooled, they were each Weighed to determine the weight gain of each specimen. From this, the weight increase per unit original area was computed for each specimen. The samples were then brushed with a wire brush to remove loose scale, and the percentage of original sample remaining was then determined. In many cases the scale proved to be tightly adherent and could not be removed entirely, which accounts for the fact that values greater than 100 are reported in several instances under percent of original sample remaining. The samples were then sectioned centrally, mounted in Bakelite, polished, and etched for microexa-mination. The thickness of unaffected base material was measured by means of a calibrated movable stage. Finally, hardness readings were taken in the center of the cross section. Values obtained in accordance with the procedures described above were as follows:

siles, for jet engine parts and for such specific uses as leading edge wing sections of high speed aircraft for upper atmosphere operation.

New and useful alloys of titanium and niobium and of titanium-niobium-base alloys having been described and characterized, it is desired to further define the invention according to the following claims.

What is claimed is:

1. Titanium-niobium alloys consisting of from about 40 percent to about 60 percent niobium, from about percent to about percent vanadium, balance titanium, said alloys being characterized by good hot hardness properties.

2. Titanium-niobium alloys consisting of from about 40 percent to about percent niobium, from about 30 percent to about 40 percent zirconium, balance titaniiun, said alloys being characterized by good hot hardness properties.

3. Titanium-niobium-base alloys of the beta-phase type consisting of from about 30 percent to about percent niobium, from about 30 percent to about 40 percent of an element from the group consisting of vanadium, zirconium, and tantalum, balance titanium.

Table V.Resistance of Ti--Nb Base Alloys to Oxidation in a Static Atmosphere 16 hours at 1,400 F. 16 hours at 1,800 13.

Composition Original weight Viekers Weight Penetra- Percent Weight Penetra Percent percent hardness increase tion of of Vickers increase tron oi 0 f V1ckers (balance Ti) (10- g per unit contamioriginal hardness per unit contarmoriginal hardness load) original nant per sample (IO-kg original nant per sample 10-kg.

area, mg./ si e, remainload) area, mg] side, remainload) sq. em. inch ing sq. cm. inch mg 138 2. 5S 0. 0063 73. 7 Total 146 3. 54 0.0063 61. 5 Total 159 6. 96 0. 0052 92. 4 Total 164 3. 0.0065 52. 9 Total 199 7. 20 0.0057 72. 6 Total 272 14. 17 O. 0040 126. 9 Total 283 172. 6 Total 171. 0 Total 304 108. 4 Total 108. 5 Total 2. 86 0. 0063 63. 4 Total 149 3. 25 0. 0060 62. 6 Total 179 4. 67 0. 0040 65. 2 Total 167 4. 31 0. 0033 72. 0 Total 50 N b-20 Zr 209 17. 44 0.0068 69. 9 Total 50 Nb-30 Zr 249 112. 1 Total 73. 0 Total From the values listed above it is apparent that 16 hours exposure at 1400 F. had no unduly severe effects on most of the alloys. Except for the Ti50 Nb--20 Zr alloy, which flaked slightly, a tightly adherent scale was formed on all the specimens. As has been noted above, this scale could not always be entirely removed by a wire brush, and consequently many of the values for percent of original sample remaining are in excess of 100.

The alloys of this invention will find many applications. They are particularly useful for structural members for high temperature applications. They are useful for mis- References Cited in the file of this patent UNITED STATES PATENTS H UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Pateni No. 3,038,798 June 12, 1962 Lewis W. Berger et a1.

It is hereby certified that error appears in the above numbered patent requiring correction and that the-said Letters Patent should read as corrected below.

" Column 3, Table 11, column 4, line 1 thereof, for

239 read 230 columns 3 and 4, Table 111, column 4, 11ne 14 thereof, for "780,000" read 78,000

Signed and sealed this 16th day of October 1962.

(SEAL) Attest:

ERNEST w. SWIDER DAVID LADD Attesting Officer Commissioner of Patents 

3. TITANIUM-NIOBIUM-BASE ALLOYS OF THE BETA-PHASE TYPE CONSISTING OF FROM ABOUT 30 PERCENT TO ABOUT 70 PERCENT NIOBIUM, FROM ABOUT 30 PERCENT TO ABOUT 40 PERCENT OF AN ELEMENT FROM THE GROUP CONSISTING OF VANADIUM, ZIRCONIUM, AND TANTALUM, BALANCE TITANIUM. 